Structural adhesives are generally thermosetting resins that may be used to replace or augment conventional joining techniques such as screws, bolts, nails, staples, rivets, welding, brazing and soldering. These structural adhesives are generally supplied as two components that are mixed just prior to application. Some examples of known structural adhesives in the industry include, for example:
U.S. Pat. App. Publication No. 2012/0029115 which relates to a room temperature curable two-part epoxy structural adhesive composition containing (A) a bisphenol A epoxy resin, a CTBN modified bisphenol A type epoxy resin and/or a core-shell polymer toughened bisphenol A type epoxy resin, a silane coupling agent, a thixotropic agent and a coloring agent, and (B) a polyamide, a polyether amine, a filler and a curing accelerator;
U.S. Pat. App. Publication No. 2011/0143061 which disclose a two-part structural adhesive that includes (A) a resin containing at least one norbornane group and at least one methacrylate containing compound, and (B) a peroxide and at least one thiol;
U.S. Pat. App. Publication No. 2011/0126980 which is directed to a two-part structural adhesive including (A) an epoxy resin and, (B) an amine curing agent and a toughening agent and oil displacing agent in either component (A) or (B);
U.S. Pat. App. Publication No. 2011/0177242 which discloses a two-part structural adhesive composition containing (A) an aromatic epoxy resin and (B) an amine curing agent and at least one ester in either component (A) or (B); and
U.S. Pat. No. 5,313,998 which relates to a two-part adhesive that includes (A) an acrylic and a peroxide and (B) a condensation reaction product of an aldehyde and amine and a copper salt and wherein an acid phosphate is added to either solution (A) or to both solutions (A) and (B).
In addition, U.S. Pat. No. 6,869,497 teaches a two part adhesive including (A) an acrylic monomer, a metal molybdate, and acrylic or methacrylic acid and (B) a peroxide while U.S. Pat. Nos. 7,348,385 and 7,479,528 teach two part adhesives containing (A) an acrylic monomer, chlorosulphonated polymer, and a peroxide and (B) a cycloheteroatom zirconate or titannate.
Known structural adhesives exhibit some shortcomings, for example, they exhibit yellowing when exposed to UV radiation, they contain hazardous peroxides, they exhibit slow cure at room temperature, and/or have less than desired sag resistance. Therefore, there is a need for a structural adhesive that is UV and sag resistant, can be tailored to a specific application, conveniently formulated, applied to one or more substrates and rapidly cured at room temperature to provide strong bonds over a desired time range.